The
issue of the rouble coins went on satisfactorily under Kankrin's
watchful guidance and under the stimulus of this demand the output of
the mines increased rapidly to some 60,000 ounces in 1830, reaching a
record of about 120,000 ounces in 1843 but then declining rapidly. This
was occasioned by a serious fall in the demand for platinum outside
Russia, causing a fall in price in the western markets and a drop in
production in Colombia. In 1843 the output there was only 1,600 ounces
and in due course the price fell to a level lower than the exchange
value of the Russian platinum coins. Kankrin, alarmed at the prospect of
extensive counterfeiting, put a severe limitation on the amounts coined
and strengthened his customs regulations at the frontiers.

Citation: Transactions of the Institution of Mining and Metallurgy, Vol. 21 (1912) p.650

Here, the Source-Spot for unprocessed 'Platinum Black' was confused with a Paris Price for refined Iridium (selling much higher.) But from 1834, it appears the Spot-Price for Platinum Black had fallen -62.22%